KR101541021B1 - Piezoelectric ceramics, manufacturing method therefor, piezoelectric element, liquid discharge head, ultrasonic motor, and dust removal device - Google Patents

Abstract

A barium titanate piezoelectric ceramic excellent in piezoelectric performance and mechanical quality factor (Q _m ) and a piezoelectric device using the piezoelectric ceramic are provided. Specifically, in a piezoelectric ceramics, crystal grains; And the grain boundaries between the crystal grains, wherein the crystal grains each contain 0.04 mass% or more and 0.20 mass% or less of manganese in terms of metal with respect to barium titanate of the perovskite type structure and barium titanate, At least one compound selected from the group consisting of Ba ₄ Ti ₁₂ O ₂₇ and Ba ₆ Ti ₁₇ O ₄₀ , wherein manganese is included in crystals contained in the grain boundaries, and when observed on the surface or cross section of the piezoelectric ceramics, The proportion of at least one compound selected from the group consisting of Ba ₄ Ti ₁₂ O ₂₇ and Ba ₆ Ti ₁₇ O ₄₀ contained in the grain boundary is 0.05 area% or more and 2 area% or more, Or less, and a piezoelectric device using the piezoelectric ceramic.

Description

TECHNICAL FIELD [0001] The present invention relates to a piezoelectric ceramic, a method of manufacturing the piezoelectric ceramic, a piezoelectric element, a liquid discharge head, an ultrasonic motor, and a dust removing device.

The present invention relates to a piezoelectric ceramic, a manufacturing method thereof, a piezoelectric element, a liquid discharge head, an ultrasonic motor, and a dust removing device. Particularly, the present invention relates to a barium titanate piezoelectric ceramics having good piezoelectric performance and mechanical quality factor (Q _m ) by controlling the composition of grain boundaries and crystal structure.

A piezoelectric ceramic generally used is an ABO ₃ type perovskite oxide such as zirconium titanate (hereinafter referred to as "PZT").

However, PZT containing lead as an A site element may cause environmental problems. For this reason, a piezoelectric ceramics using a perovskite-type oxide not containing lead is required.

Barium titanate is known as a piezoelectric ceramics material of a non-perovskite type. Patent Document 1 discloses barium titanate produced by a resistance heating / two-step sintering method. It is described that when a nano-sized barium titanate powder is sintered by the above two-step sintering method, a ceramic excellent in piezoelectric characteristics can be obtained. However, the ceramics obtained by the above two-step sintering method are not suitable for use in resonance devices because of their low mechanical coefficient of quality and low durability at high temperatures.

Patent Document 2 discloses a ceramic in which a part of the barium titanate barium site is substituted with calcium and further manganese, iron or copper is added. In the patent literature, it is described that the ceramic has an excellent mechanical quality coefficient by manganese, iron or copper. However, by increasing the amount of calcium, the temperature of the crystal phase transition shifts to about -50 占 폚, so that the piezoelectric property remarkably decreases.

It is well known that when manganese is added in an increased amount, manganese oxide (MnO _x ) precipitates in addition to barium titanate crystal grains. Since the manganese oxide does not have a dielectric property, the piezoelectric performance of the ceramic is deteriorated. Furthermore, the above-mentioned manganese oxide lowers the mechanical quality factor because the valence of manganese is unstable.

In other words, barium titanate piezoelectric ceramics is expected to have both good piezoelectric performance and high mechanical quality factor.

Patent Document 1: JP-A-2008-150247 Patent Document 2: JP-A-2010-120835

The present invention has been made in order to overcome such a problem. An object of the present invention is to provide a piezoelectric ceramics having good piezoelectric performance and mechanical quality factor (Q _m ) by controlling the composition of grain boundaries and crystal structure, and a method for producing the same.

It is another object of the present invention to provide a piezoelectric element, a liquid discharge head, an ultrasonic motor, and a dust removing device each using the piezoelectric ceramics.

A piezoelectric ceramic for solving the above-mentioned problems is characterized in that in a piezoelectric ceramics, crystal grains; And the grain boundaries between the crystal grains, wherein the crystal grains each contain 0.04 mass% or more and 0.20 mass% or less of manganese in terms of metal with respect to barium titanate of the perovskite type structure and barium titanate, At least one compound selected from the group consisting of Ba ₄ Ti ₁₂ O ₂₇ and Ba ₆ Ti ₁₇ O ₄₀ , wherein manganese is included in crystals contained in the grain boundaries, and when observed on the surface or cross section of the piezoelectric ceramics, The proportion of at least one compound selected from the group consisting of Ba ₄ Ti ₁₂ O ₂₇ and Ba ₆ Ti ₁₇ O ₄₀ contained in the grain boundary is 0.05 area% or more and 2 area% or more, Or less.

A process for producing a piezoelectric ceramic for solving the above-mentioned problems comprises a step of adding a binder to barium titanate particles each containing 0.04 mass% or more and 0.20 mass% or less of manganese in terms of metal, to prepare a granulated powder; And adding at least one compound selected from the group consisting of Ba ₄ Ti ₁₂ O ₂₇ and Ba ₆ Ti ₁₇ O ₄₀ particles to the granulated powder, and sintering the mixture.

In addition, a method of manufacturing a piezoelectric ceramic for solving the above-mentioned problems comprises a step of adding a binder to barium titanate particles each containing 0.04 mass% or more and 0.20 mass% or less of manganese in terms of metal, And a step of sintering the mixture prepared by adding titanium oxide particles each having an average particle size of 100 nm or less to the granulated powder.

According to an aspect of the present invention, there is provided a piezoelectric element comprising: a first electrode; Piezoelectric ceramics; And a second electrode, wherein the piezoelectric ceramics includes the piezoelectric ceramics described above.

The liquid discharge head for solving the above-mentioned problems is a liquid discharge head using the piezoelectric element.

An ultrasonic motor for solving the above problems is an ultrasonic motor using the piezoelectric element.

A dust removing apparatus for solving the above-mentioned problems is a dust removing apparatus using the piezoelectric element.

According to the present invention, it is possible to provide a piezoelectric ceramic excellent in piezoelectric performance and mechanical quality factor (Q _m ) by controlling the composition of grain boundaries and the crystal structure, and a method for producing the same. Further, according to the present invention, it is possible to provide a piezoelectric element, a liquid discharge head, and an ultrasonic motor each using the piezoelectric ceramics.

Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1A is a schematic view showing an embodiment of the configuration of a liquid discharge head of the present invention. FIG.
1B is a schematic view showing an embodiment of the configuration of the liquid discharge head of the present invention.
2A is a schematic view showing an embodiment of the configuration of the ultrasonic motor of the present invention.
2B is a schematic view showing an embodiment of the configuration of the ultrasonic motor of the present invention.
3A is a schematic view showing an embodiment of the dedusting device of the present invention.
3B is a schematic view showing an embodiment of the dedusting device of the present invention.
FIG. 4A is a schematic view showing the configuration of the piezoelectric element of the present invention in FIG. 3A and FIG. 3B, respectively. FIG.
Fig. 4B is a schematic view showing the configuration of the piezoelectric element of the present invention in Fig. 3A and Fig. 3B, respectively.
Fig. 4C is a schematic view showing the configuration of the piezoelectric element of the present invention in Figs. 3A and 3B, respectively. Fig.
5 is a pattern showing the principle of oscillation of the dedusting device of the present invention.
6 is a conceptual view showing an embodiment of the piezoelectric ceramic of the present invention.
7A is a SEM secondary electron image of the surface of the piezoelectric ceramics of the present invention.
7B is a TEM observation of the piezoelectric ceramics of the present invention.
8A is a [100] incident electron beam diffraction pattern of Ba ₄ Ti ₁₂ O ₂₇ calculated from document data.
Fig. 8B is an electron diffraction pattern of a bipaverite-type structure at the grain boundaries of the piezoelectric ceramics of the present invention. Fig.
9A is an [011] incident electron diffraction pattern of Ba ₆ Ti ₁₇ 0 ₄₀ calculated from document data.
Fig. 9B is an electron diffraction pattern of a bipaverite-type structure at the grain boundaries of the piezoelectric ceramics of the present invention. Fig.

Hereinafter, embodiments of the present invention will be described.

A piezoelectric ceramics according to the present invention comprises: crystal grains; And a grain boundary between the crystal grains, wherein each of the crystal grains contains 0.04 mass% or more and 0.20 mass% or less of manganese in terms of metal with respect to barium titanate of the perovskite type structure and barium titanate, At least one compound selected from the group consisting of Ba ₄ Ti ₁₂ O ₂₇ and Ba ₆ Ti ₁₇ O ₄₀ .

As used herein, the term "ceramic" refers to aggregates (also referred to as bulk bodies) of crystal grains sintered by heat treatment, or so-called polycrystalline, whose main component is a metal oxide. The term includes those processed after sintering. However, slurries in which powders or powders are dispersed are not included in this term.

The perovskite-type barium titanate is BaTiO ₃ . The barium titanate may contain not only manganese but also other property-adjusting components and manufacturing impurities.

In the piezoelectric ceramics according to the present invention, the biparbovite structure compound exists in the grain boundaries of the crystal grains other than the barium titanate crystal grains of the perovskite type structure. The compound of the biparovskite structure is at least one compound selected from Ba ₄ Ti ₁₂ O ₂₇ and Ba ₆ Ti ₁₇ O ₄₀ .

In the present specification, at least one compound selected from Ba ₄ Ti ₁₂ O ₂₇ and Ba ₆ Ti ₁₇ O ₄₀ existing in the crystal grains is referred to as "sub-grains".

The Ba ₄ Ti ₁₂ O ₂₇ belongs to the space group C 2 / m and has a dielectric property. Further, the Ba ₆ Ti ₁₇ O ₄₀ belongs to the space group A 2 / a and has a dielectric property.

As used herein, the term "grain boundary" refers to an interface between crystal grains (this includes cases where crystal grains are in contact with each other linearly and intermittently). Furthermore, in the following description, a surface or a line where two crystal grains are brought into contact with each other in the "grain boundary" is also referred to as a "boundary". In the following description, a place where three or more crystal grains intersect at one point or a line in a "grain boundary" is referred to as a "triple point" (the boundary of three needle-like crystal grains intersects with a "line" ).

Fig. 6 is a conceptual diagram showing one embodiment of the piezoelectric ceramics of the present invention, and schematically shows the relationship between crystal grains, grain boundaries and sub-grains. 401 is a crystal grain of barium titanate. The crystal grains are in contact with each other via at least one of the boundary and the triple point. 402 denotes a boundary between crystal grains, and 403 denotes a triple point. And reference numeral 404 denotes a sub-particle existing at a boundary between crystal grains. In the piezoelectric ceramics of the present invention, at least one compound selected from Ba ₄ Ti ₁₂ O ₂₇ and Ba ₆ Ti ₁₇ O ₄₀ exists as sub-grains in the grain boundary (boundary or triple point) of the crystal grains. In the figure, reference numerals 405 and 406 represent at least one sub particle of Ba ₄ Ti ₁₂ O ₂₇ and Ba ₆ Ti ₁₇ 0 ₄₀ existing at the triple point.

As a method of easily distinguishing the crystal grains from the sub-grains, a method using a scanning electron microscope (SEM) is known. This method utilizes the fact that the crystal grains and the sub-grains are observed with different contrast by the user when the surface of the piezoelectric ceramics is observed with the SEM secondary electron image.

7A is a SEM secondary electron image obtained by observing the piezoelectric ceramic surface of the present invention. What is revealed by this electron is that the subpixels existing in the triple point 502 and the crystal grain 501 can be observed with different contrast. Fig. 7B shows a part of the piezoelectric ceramics including the sub-particles obtained by a transmission electron microscope (TEM). It is noted that by TEM observation, it is possible to distinguish a part of the sub particle 504 from a part of the crystal particle 503.

The barium (Ba) site of the barium titanate (BaTiO ₃ ) may be partially substituted with another bivalent metal or a pseudobaric metal. Examples of the divalent metal that can substitute the Ba site include Ca and Sr. As the pseudo-divalent metal that can replace the Ba _{site, (Bi 0.5 Na 0.5),} (Bi 0.5 K 0.5), (Bi 0.5 Li 0.5), (La 0.5 Na 0.5), (La 0.5 K 0.5), (La _0.5 Li _0.5 ). When the Ba site is partially substituted with another bivalent metal or pseudobaric metal, the replacement ratio is 20 atm% or less, preferably 10 atm% or less. If the substitution ratio exceeds 20 atm%, there is a possibility that the piezoelectric characteristics inherent to barium titanate can not be sufficiently obtained.

The titanium (Ti) site of barium titanate (BaTiO ₃ ) may be partially substituted with another tetravalent metal or a pseudo tetravalent metal. Examples of the tetravalent metal capable of substituting the Ti site include Zr, Hf, Si, Sn, and Ge. Examples of the pseudo-tetravalent metal capable of substituting the Ti site include a combination of a divalent metal and a ^pentavalent metal (M ²⁺ _1/3 M ⁵⁺ _2/3 ), a combination of a ^trivalent metal and a ^pentavalent metal (M ^{3 +} _1/2 M ⁵⁺ _1/2 ), a combination of a trivalent metal and a ^hexavalent metal (M ³⁺ _2/3 M ⁶⁺ _1/3 ), and the like.

In the piezoelectric ceramics of the present invention, the crystal grains contain 0.04 mass% or more and 0.20 mass% or less, preferably 0.05 mass% or more and 0.17 mass% or less of manganese in terms of metal with respect to barium titanate. If the piezoelectric ceramics whose main component is barium titanate contains the above-mentioned manganese component, the piezoelectric ceramic can be provided with improved insulation or a mechanical quality factor (Q _m ). When the content of manganese is less than 0.04 mass% with respect to the barium titanate, the mechanical quality factor of the piezoelectric ceramic can not be sufficiently improved. On the other hand, when the content of manganese is larger than 0.20 mass%, there is a possibility that the hexagonal barium titanate and impurity phases which are inferior to the piezoelectric properties are mixed. Therefore, the piezoelectric performance of the entire piezoelectric ceramics may become insufficient.

Ba ₄ Ti ₁₂ O ₂₇ or Ba ₆ Ti ₁₇ O _{40, which} is a compound constituting the sub-particles contained in the grain boundaries, can be obtained by, for example, a method of obtaining the above compound by a limited field diffraction method using a transmission electron microscope Can be specified by comparing the diffraction image with the data in the known literature.

The limited field diffraction method is a method of observing a diffraction pattern of only a specific region of the magnified image observed by a transmission electron microscope (TEM). It is possible to observe only the diffraction pattern generated from the above compound by using this method.

The sub-particles may fill voids that may be formed in grain boundaries between crystal grains. In the case where the sub-particles formed of at least one of Ba ₄ Ti ₁₂ O ₂₇ and Ba ₆ Ti ₁₇ O _40, which are dielectrics, fill the voids, the dielectric constant of the piezoelectric ceramics can be made higher than that in the state where voids exist. That is, the filling of the voids by the sub-particles can improve the piezoelectric characteristics of the piezoelectric ceramics.

In the piezoelectric ceramics of the present invention, the ratio of at least one compound selected from the group consisting of Ba ₄ Ti ₁₂ O ₂₇ and Ba ₆ Ti ₁₇ O ₄₀ contained in the grain boundaries when observed on the surface or cross section of the piezoelectric ceramics, Is preferably not less than 0.05% by area and not more than 1% by area, preferably not less than 0.1% by area and not more than 0.5% by area, based on the total area of the surface or cross section of the piezoelectric ceramics.

If the content of Ba ₄ Ti ₁₂ O ₂₇ or Ba ₆ Ti ₁₇ 0 _{40 in} the grain boundary, that is, the ratio of the minor grains in the entire piezoelectric ceramics is less than 0.05 area%, the precipitation of manganese oxide in the grain boundary can not be completely prevented There is a concern. Therefore, there is a possibility that a high piezoelectric performance inherent to barium titanate can not be obtained sufficiently. When the ratio of the sub-particles contained in the grain boundaries is larger than 1% by area, sub-particles having no piezoelectricity are excessively precipitated in the grain boundaries. Therefore, there is a possibility that a high piezoelectric performance inherent to barium titanate can not be sufficiently obtained.

The ratio of the sub-particles contained in the grain boundaries of the piezoelectric ceramics can be calculated, for example, by a method using the scanning electron microscope described above. The surface or cross-section of the piezoelectric ceramics containing manganese is observed using a reflection electron image of a scanning electron microscope. In the above observation method, the sub-particles and the crystal grains of the piezoelectric ceramics are observed with different contrast. Therefore, the sub-particles and the crystal grains of the piezoelectric ceramics are distinguished from each other, and the ratio of the sub-grains is calculated by measuring the area ratio of both grains.

The piezoelectric ceramic of the present invention, the grain boundary Ba ₄ Ti ₁₂ 0 ₂₇ or all of Ba ₆ Ti ₁₇ containing 0 _{to 40,} and the Ba ₄ Ti ₁₂ 0 ₂₇ and Ba ₆ Ti ₁₇ 0 ₄₀ is preferred to contain Mn Do.

In general, when manganese is added to a piezoelectric ceramics, all of the manganese added is not always present in the crystal grains. When manganese is added to the conventional piezoelectric ceramics, manganese added as manganese oxide (MnOx) exists in the grain boundary.

In the piezoelectric ceramics containing the manganese oxide at grain boundaries, the manganese oxide has no property as a dielectric and degrades the insulating property of the piezoelectric ceramics, so that the piezoelectric performance also deteriorates. Further, the manganese oxide exists in the grain boundary or outside the crystal grains, and the valence of manganese is also unstable. Therefore, the manganese oxide decreases the mechanical quality factor of the piezoelectric ceramics.

On the other hand, in the piezoelectric ceramics of the present invention, at least one compound selected from sub-particles of Ba ₄ Ti ₁₂ O ₂₇ and Ba ₆ Ti ₁₇ O ₄₀ exists in the grain boundary.

Since Ba ₄ Ti ₁₂ O ₂₇ and Ba ₆ Ti ₁₇ O ₄₀ are dielectrics, the presence of such a compound in the grain boundary does not cause deterioration of the insulation of the piezoelectric ceramics. In addition, a state in which manganese oxide does not exist in the grain boundaries can be established by adding manganese present in the grain boundaries as the manganese oxide to the sub-grains. As a result, it is possible to prevent a reduction in piezoelectric performance and a mechanical quality factor due to the above-described manganese oxide.

Therefore, in the piezoelectric ceramic of the present invention, Ba ₄ Ti ₁₂ O ₂₇ or Ba ₆ Ti ₁₇ O ₄₀ contained in the grain boundary preferably contains manganese.

In the piezoelectric ceramics of the present invention, the content of manganese in at least one compound selected from the group consisting of Ba ₄ Ti ₁₂ O ₂₇ and Ba ₆ Ti ₁₇ O ₄₀ contained in the grain boundaries is in the range of Ba ₄ Ti ₁₂ O ₂₇ and At least one compound selected from the group consisting of Ba ₆ Ti ₁₇ 0 ₄₀ is preferably not less than 0.6 mass% and not more than 2.8 mass%, more preferably not less than 1.0 mass% nor more than 2.0 mass% in terms of metal.

When the content of manganese is less than 0.6 mass%, that is, when the capacity of manganese dissolved as at least one solid solution of Ba ₄ Ti ₁₂ O ₂₇ and Ba ₆ Ti ₁₇ O ₄₀ is small, manganese A compound containing manganese as a main component such as manganese oxide may precipitate at the grain boundary.

Further, when the content of manganese is more than 2.8 mass%, that is, when the capacity of manganese dissolved as at least one solid solution of Ba ₄ Ti ₁₂ O ₂₇ and Ba ₆ Ti ₁₇ O ₄₀ is large, The capacity of manganese is reduced. Therefore, there is a possibility that the piezoelectric ceramics can not obtain a sufficient mechanical quality coefficient.

The content of manganese can be determined, for example, when the grain boundary is observed by the limited field diffraction method and the region defined by any one of the crystal structures of Ba ₄ Ti ₁₂ O ₂₇ or Ba ₆ Ti ₁₇ O ₄₀ , It may be specified from the analysis result obtained by the spectroscopic method.

In the piezoelectric ceramic of the present invention, it is preferable to contain the grain boundary Ba ₄ Ti ₁₂ 0 ₂₇ and Ba ₆ Ti ₁₇ containing 0 _{to 40,} and the Ba ₄ Ti ₁₂ 0 ₂₇ and Ba ₆ Ti ₁₇ 0 ₄₀ each Mn .

When the grain boundary is occupied by Ba ₄ Ti ₁₂ O ₂₇ and Ba ₆ Ti ₁₇ O ₄₀ , the dielectric constant of the entire piezoelectric ceramics is improved and the piezoelectric performance is improved. The manganese dissolved as a solid solution in the crystal grains of Ba ₄ Ti ₁₂ O ₂₇ and Ba ₆ Ti ₁₇ O ₄₀ is a compound containing Mn as a main component such as manganese oxide (MnO), and precipitates .

In the piezoelectric ceramic of the present invention, it is preferable that the content ratio of manganese contained in Ba ₄ Ti ₁₂ O ₂₇ is larger than the content ratio of manganese contained in Ba ₆ Ti ₁₇ 0 ₄₀ . The content ratio of manganese contained in each of Ba ₄ Ti ₁₂ O ₂₇ and Ba ₆ Ti ₁₇ O ₄₀ can be evaluated by combining the crystal structure determined by the limited viewing angle method described above with the energy dispersive spectroscopy have.

By containing a large amount of manganese in Ba ₄ Ti ₁₂ 0 ₂₇ , the insulating property and sintering density are improved.

The "particle size" of the piezoelectric ceramics used in this specification refers to a so-called "projected area diameter" in the microscopic observation method and refers to the diameter of a perfect circle having the same area as the projected area of the crystal grains. In the present invention, the method of measuring the particle diameter is not particularly limited. For example, the particle size may be obtained by subjecting a photographic image obtained by photographing the surface of the piezoelectric ceramic with a polarizing microscope or a scanning electron microscope to image processing. An example of the enlargement magnification when determining the grain size of the crystal grains is about 5 to 5,000 times. One of an optical microscope and an electron microscope may be appropriately used depending on the magnification. The grain size may be obtained from the image of the polished surface or the cross section rather than the surface of the ceramic.

Next, a method of manufacturing the piezoelectric ceramics of the present invention will be described.

A first aspect of a method for producing a piezoelectric ceramic according to the present invention comprises the steps of: preparing a granulated powder by adding a binder to barium titanate particles each containing 0.04 mass% or more and 0.20 mass% or less of manganese in terms of metal; And a step of sintering the mixture prepared by adding at least one compound selected from Ba ₄ Ti ₁₂ O ₂₇ and Ba ₆ Ti ₁₇ O ₄₀ particles to the granulated powder.

The barium titanate particles each containing manganese may contain barium titanate, other property adjusting components other than manganese, and impurities in the synthesis phase. Examples of the impurities include metal-derived components such as aluminum, calcium, niobium, iron and lead, glass components, and hydrocarbon-based organic components. The content of the impurity is preferably 5 mass% or less, and more preferably 1 mass% or less.

The average particle diameter of the primary particles of barium titanate particles containing manganese, respectively, is not particularly limited. However, in order to obtain a high-density and homogeneous piezoelectric ceramics, the preferred average primary particle diameter is 5 nm or more and 300 nm or less, preferably 50 nm or more and 150 nm or less. If the average particle diameter of the primary particles is excessively small or excessively large, the density of the ceramic after sintering may become insufficient. Here, "primary particle" represents a minimum unit of the particles constituting the powder, which can be clearly distinguished from the others. Primary particles may aggregate to form larger secondary particles. A secondary particle may be intentionally formed by an assembling process using a polymer binder.

A method for producing barium titanate particles each containing manganese and a method for producing a granular component including adding a binder to barium titanate particles each containing manganese are not particularly limited.

In the case of barium titanate with manganese attached thereto, a manganese component may be added to commercially available or synthesized barium titanate particles in a post-process. The method of adding the manganese component is not limited. However, it is preferable that the manganese component is uniformly adhered to the surface of barium titanate. In that respect, the most preferred addition method is the spray drying method. The spray drying method is preferable from the viewpoint that a granulated powder can be produced by adding a binder at the same time as the manganese component is adhered and that the particle diameter can be made more uniform.

In the case of barium titanate dissolved as a solid solution of manganese, the barium titanate precursor containing the manganese component may be crystallized. For example, an equimolar mixture of a barium compound and a titanium compound is prepared, and then a desired amount of manganese component is added to the mixture. Subsequently, the mixture is calcined at about 1000 DEG C to obtain barium titanate particles in which the manganese component is dissolved as a solid solution.

Also in this case, the method of producing the granules is not particularly limited. However, from the viewpoint that the particle diameter can be more uniform, the spray drying method is preferable.

Examples of the binder that can be used for granulation include polyvinyl alcohol (PVA), polyvinyl butyral (PVB), and acrylic resin. The amount of the binder added is preferably 1% by mass to 10% by mass, more preferably 2% by mass to 5% by mass from the viewpoint of increasing the density of the molded article.

Examples of barium compounds that may be used in producing barium titanate particles each containing manganese include barium carbonate, barium oxalate, barium oxide, barium acetate, barium nitrate, barium aluminate, and various barium alkoxides .

An example of a titanium compound that can be used for barium titanate particles each containing manganese is titanium oxide.

Examples of the manganese component which may be used in the barium titanate particles each containing manganese include manganese compounds such as manganese oxide, manganese dioxide, manganese acetate and manganese carbonate.

In the piezoelectric ceramics which can be obtained by sintering a mixture obtained by adding at least one of Ba ₄ Ti ₁₂ O ₂₇ particles or Ba ₆ Ti ₁₇ O ₄₀ particles to the granulated powder, the Ba ₄ Ti ₁₂ O ₂₇ At least one of the particles and Ba ₆ Ti ₁₇ O ₄₀ particles precipitates. With the above-described mechanism, such piezoelectric ceramics can keep Mn in the crystal grains, and can satisfy the piezoelectric performance and the mechanical quality factor. The addition amount of each of the Ba ₄ Ti ₁₂ O ₂₇ particles and Ba ₆ Ti ₁₇ O ₄₀ particles is 0.02 mass% or more and 1.5 mass% or less. That is, according to the production method A, Ba ₄ Ti ₁₂ O ₂₇ particles or Ba ₆ Ti ₁₇ O ₄₀ particles can be precipitated without fail.

The mixed barium titanate particles are molded into a desired shape and then sintered to form a ceramic.

The sintering method of the ceramics in the above production method is not limited. Examples of the sintering method include sintering by an electric furnace, energization heating method, microwave sintering method, radio wave sintering method of millimeter, hot isostatic pressing (HIP), and the like.

The sintering temperature of the ceramics in the above production method is not limited, but is preferably a temperature at which barium titanate sufficiently grows crystals. Therefore, the preferable sintering temperature is 1000 占 폚 to 1450 占 폚, and more preferably 1300 占 폚 to 1400 占 폚. The sintered barium titanate ceramic in this temperature range exhibits good piezoelectric performance.

In order to stabilize the characteristics of the piezoelectric ceramics obtained by the sintering treatment with high reproducibility, it is preferable to carry out the sintering treatment for about 1 hour to 12 hours while keeping the sintering temperature constant within the above range.

A second aspect of the method for producing a piezoelectric ceramic according to the present invention comprises the steps of: preparing a granulated powder by adding a binder to barium titanate particles each containing 0.04 mass% or more and 0.20 mass% or less of manganese in terms of metal; And a step of sintering the mixture prepared by adding titanium oxide particles each having an average particle diameter of 100 nm or less to the granulated powder.

The barium titanate particles each containing manganese may contain barium titanate and characteristic adjusting components other than manganese and impurities in the synthesis phase. Examples of the impurities include metal-derived components such as aluminum, calcium, niobium, iron and lead, glass components, and hydrocarbon-based organic components. The content of the impurity is preferably 5 mass% or less, and more preferably 1 mass% or less.

The average particle diameter of the primary particles of the barium titanate particles each containing manganese is not particularly limited. However, in order to obtain a high-density and uniform piezoelectric ceramics, the average primary particle size is preferably 5 nm or more and 300 nm or less, and more preferably 50 nm or more and 150 nm or less. If the average particle diameter of the primary particles is excessively small or too large, the density of the ceramic after sintering may become insufficient. Here, "primary particles" refers to the smallest unit of the particles constituting the powder, which can be clearly distinguished from the others. The primary particles may aggregate to form larger secondary particles. Secondary particles may be intentionally formed by an assembling process using a polymer binder.

A production method of producing barium titanate particles each containing manganese and a method of assembling a powder including adding a binder to barium titanate particles each containing manganese is not particularly limited.

In the case of barium titanate to which manganese is attached, manganese components may be added to commercially available or synthesized barium titanate particles in a post-process. The method of adding the manganese component is not limited. However, it is preferable that the manganese component is uniformly adhered to the surface of barium titanate. In that respect, the most preferred addition method is the spray drying method. The spray-drying method is preferable from the viewpoint that granules can be prepared by adding a binder at the same time as the manganese component is adhered, and that the particle diameter can be more uniform.

In the case of barium titanate dissolved as a solid solution of manganese, the barium titanate precursor containing the manganese component may be crystallized. For example, a equimolar mixture of a barium compound and a titanium compound is prepared, and then a desired amount of manganese component is added to the mixture. Subsequently, this mixture is calcined at about 1000 캜 to obtain barium titanate particles in which the manganese component is dissolved as a solid solution. Also in this case, the method of producing the granulated powder is not particularly limited. However, from the viewpoint that the particle diameter can be more uniform, the spray drying method is preferable.

Examples of the binder which can be used for the assembly include polyvinyl alcohol (PVA), polyvinyl butyral (PVB) and acrylic resin. The amount of the binder added is preferably 1% by mass to 10% by mass, more preferably 2% by mass to 5% by mass from the viewpoint of increasing the density of the molded article.

Examples of barium compounds that may be used in producing barium titanate particles each containing manganese include barium carbonate, barium oxalate, barium oxide, barium acetate, barium nitrate, barium aluminate, and various barium alkoxides .

An example of a titanium compound that can be used for barium titanate particles each containing manganese is titanium oxide.

Examples of the manganese component which may be used in the barium titanate particles each containing manganese include manganese compounds such as manganese oxide, manganese dioxide, manganese acetate and manganese carbonate.

The manufacturing method includes sintering the mixture prepared by adding the titanium oxide particles to the granules. That is, the mixture is in a state in which the ratio of the presence ratio of titanium is larger than that of barium. However, the primary component obtained by sintering the mixture of barium titanate (Ba: Ti = 1: 1 ) is due, the excess titanium is large Ba than Ti exists ratio Ba ₄ Ti ₁₂ 0 ₂₇ particles or Ba ₆ Ti ₁₇ 0 ₄₀ And is precipitated at the grain boundaries as particles. Here, the titanium oxide particles have an average particle diameter of 100 nm or less. The titanium oxide particles each have an average particle diameter of 100 nm or less, so that the titanium oxide particles are excellent in dispersibility with the mixture B and more uniformly mixed. With the above-described mechanism, such piezoelectric ceramics can make Mn stay in the crystal grains and satisfy both the piezoelectric performance and the mechanical quality factor. The preferable addition amount of the titanium oxide particles is 0.02 mass% or more and 1.5 mass% or less. That is, by the above-described production method, Ba ₄ Ti ₁₂ O ₂₇ particles or Ba ₆ Ti ₁₇ O ₄₀ particles can be relatively easily precipitated at the grain boundaries.

Hereinafter, a piezoelectric device using the piezoelectric ceramics of the present invention will be described.

A piezoelectric element according to the present invention is a piezoelectric element having at least a first electrode, a piezoelectric ceramic and a second electrode, and the piezoelectric ceramic is the piezoelectric ceramics described above.

Each of the first electrode and the second electrode is formed of a conductive layer having a thickness of about 5 nm to 2000 nm. The material of the conductive layer is not particularly limited, and may be a material generally used for a piezoelectric element. Examples of such materials include metals such as Ti, Pt, Ta, Ir, Sr, In, Sn, Au, Al, Fe, Cr, Ni, Pd, Ag and Cu and oxides of these metals. Each of the first electrode and the second electrode may be formed of one of these, or two or more of them may be laminated. The first electrode and the second electrode may be formed of different materials.

The manufacturing method of the first electrode and the second electrode is not limited. The first electrode and the second electrode may be formed by baking the metal paste, or may be formed by sputtering, vapor deposition, or the like. Both the first electrode and the second electrode may be patterned in a desired shape.

Each of Figs. 1A and 1B is a schematic view showing one embodiment of the configuration of the liquid discharge head of the present invention. As shown in Figs. 1A and 1B, the liquid discharge head of the present invention is a liquid discharge head having the piezoelectric element 101 of the present invention. The piezoelectric element 101 is a piezoelectric element having at least a first electrode 1011, a piezoelectric ceramic 1012 and a second electrode 1013. The piezoelectric ceramics 1012 are patterned as required, as shown in Fig. 1B.

1B is a schematic view of a liquid discharge head. The liquid discharge head includes a discharge port 105, a separate liquid chamber 102, a communication hole 106 connecting the individual liquid chamber 102 and the discharge port 105, a liquid chamber separation wall 104, a common liquid chamber 107, 103, and a piezoelectric element 101. Although each of the piezoelectric elements 101 is rectangular in the figure, the shape thereof may be an elliptical shape other than a rectangular shape, a circular shape, or a parallelogram shape. In general, the piezoelectric ceramics 1012 are each in a shape corresponding to the shape of the individual liquid chamber 102.

The vicinity of the piezoelectric element 101 in the liquid discharge head of the present invention will be described in detail with reference to FIG. 1A. FIG. 1A is a cross-sectional view of a piezoelectric element in the width direction of the liquid discharge head shown in FIG. 1B. FIG. The cross-sectional shape of the piezoelectric element 101 is shown as a rectangle, and may be trapezoidal or inverted trapezoidal.

In this figure, the first electrode 1011 is used as the lower electrode, and the second electrode 1013 is used as the upper electrode. However, the arrangement of the first electrode 1011 and the second electrode 1013 is not limited to that described above. For example, the first electrode 1011 may be used as a lower electrode or as an upper electrode. Similarly, the second electrode 1013 may be used as the upper electrode or as the lower electrode. The buffer layer 108 may be present between the diaphragm 103 and the lower electrode.

At this time, the difference in the names is due to the manufacturing method of the device, and in either case, the effect of the present invention can be obtained.

In the liquid discharge head, the diaphragm 103 fluctuates up and down by the expansion and contraction of the piezoelectric ceramics 1012 to apply pressure to the liquid in the individual liquid chamber 102. As a result, the liquid is discharged from the discharge port 105. The liquid discharge head of the present invention can be used for a printer application or an electronic device.

The thickness of the diaphragm 103 is not less than 1.0 μm and not more than 15 μm, preferably not less than 1.5 μm and not more than 8 μm. The diaphragm material is not limited, but is preferably Si. B or P may be doped in Si of the diaphragm. Further, the buffer layer and the electrode layer of the diaphragm may be part of the diaphragm.

The thickness of the buffer layer 108 is 5 nm or more and 300 nm or less, preferably 10 nm or more and 200 nm or less.

The size of the discharge port 105 is 5 占 퐉 or more and 40 占 퐉 or less from the viewpoint of the circle equivalent diameter. The shape of the discharge port 105 may be a circle, a star, a square, or a triangle.

Next, an ultrasonic motor using the piezoelectric element of the present invention will be described.

2A and 2B are schematic views showing an embodiment of the configuration of the ultrasonic motor of the present invention.

2A shows an ultrasonic motor in which the piezoelectric element of the present invention is formed into a single plate. The ultrasonic motor includes a vibrator 201 and a rotor 202 which is in contact with the sliding surface of the vibrator 201 with a pressing force by a pressing spring (not shown) And has an output shaft 203. The vibrator 201 includes an elastic ring 2011 of a metal, a piezoelectric element 2012 of the present invention, an organic adhesive 2013 for bonding the piezoelectric element 2012 to the elastic ring 2011 (for example, Crepe-based adhesive). The piezoelectric element 2012 of the present invention is formed of a piezoelectric ceramics sandwiched between a first electrode (not shown in the figure) and a second electrode (not shown).

When two alternating voltages different in phase by? / 2 are applied to the piezoelectric element of the present invention, bending waves are generated in the vibrator 201, so that each point on the slide surface of the vibrator 201 performs an elliptical motion. When the rotor 202 is pressed against the sliding surface of the vibrator 201, the rotor 202 receives the frictional force from the vibrator 201 and rotates in the direction opposite to the bending propagation wave. The driven member (not shown) is joined to the output shaft 203 and driven by the rotational force of the rotor 202.

When a voltage is applied to the piezoelectric ceramics, the piezoelectric ceramic expands and contracts by the piezoelectric transverse effect. When an elastic body such as metal is bonded to the piezoelectric element, the elastic body is bent by the expansion and contraction of the piezoelectric ceramic. The ultrasonic motor of the kind described here uses this principle.

Next, an ultrasonic motor including a piezoelectric element having a laminated structure is illustrated in Fig. 2B. The vibrator 204 is formed of a laminated piezoelectric element 2042 sandwiched between tubular metal elastic members 2041. [ The laminated piezoelectric element 2042 is a device formed of a plurality of laminated piezoelectric ceramics (not shown), and has a first electrode and a second electrode on the laminated outer surface, and an inner electrode on the laminated inner surface. The metal elastic body 2041 may be fastened by a bolt, and the piezoelectric element 2042 may be inserted and fixed by the metal elastic body. Thus, the vibrator 204 is formed.

By applying alternating voltages having different phases to the piezoelectric element 2042, the vibrator 204 excites two mutually orthogonal vibrations. These two vibrations are combined to form a circular vibration for driving the tip of the vibrator 204. [ At this time, a constricted circumferential groove is formed in the upper portion of the vibrator 204 to enlarge the displacement of the vibration for driving.

The rotor 205 is pressed against the vibrator 204 by the spring 206 for pressurization and obtains a frictional force for driving. The rotor 205 is rotatably supported by a bearing.

Next, a dust removing apparatus using the piezoelectric element of the present invention will be described.

3A and 3B are schematic views showing an embodiment of the dedusting device of the present invention.

The dust removing apparatus 310 includes a planar piezoelectric element 330 and a diaphragm 320. The material of the diaphragm 320 is not limited. When the dust removing apparatus 310 is used in an optical device, a light transmitting material or a light reflecting material can be used as the material of the diaphragm 320.

Figs. 4A to 4C are schematic diagrams showing the configuration of the piezoelectric element 330 shown in Figs. 3A and 3B. Fig. 4A and 4C show a front surface configuration and a back surface configuration of the piezoelectric element 330, respectively. Fig. 4B shows a side structure. 4A to 4C, the piezoelectric element 330 includes a piezoelectric ceramic 331, a first electrode 332 and a second electrode 333, and the first electrode 332, 2 are disposed so as to face the surface of the piezoelectric ceramic 331. [ In Fig. 4C, the front surface of the piezoelectric element 330 provided with the first electrode 332 is referred to as a first electrode surface 336. Fig. In Fig. 4A, the front surface of the piezoelectric element 330 provided with the second electrode 333 is referred to as a second electrode surface 337. Fig.

Here, the electrode surface in the present invention refers to a surface of a piezoelectric element provided with an electrode. For example, the first electrode 332 may be extended to the second electrode surface 337 as shown in Figs. 4A to 4C.

The piezoelectric element 330 and the diaphragm 320 are fixed to the first electrode surface 336 of the piezoelectric element 330 with the plate surface of the diaphragm 320, as shown in Figs. 3A and 3B. When the piezoelectric element 330 is driven, a stress is generated between the piezoelectric element 330 and the diaphragm 320 to generate an out-of-plane vibration on the diaphragm. The dust removing apparatus 310 of the present invention is a device for removing foreign matter such as dust adhering to the surface of the diaphragm 320 by the out-of-plane vibration of the diaphragm 320. [ The out-of-plane vibration means elastic vibration that moves the diaphragm in the direction of the optical axis, that is, the thickness direction of the diaphragm.

5 is a schematic view showing the principle of oscillation of the dedusting device 310 of the present invention. 5 shows a state in which an alternating electric field of the same phase is applied to the pair of left and right piezoelectric elements 330 and an out-of-plane vibration is generated in the diaphragm 320. In FIG. The polarizing direction of the piezoelectric ceramics constituting the pair of left and right piezoelectric elements 330 is the same as the thickness direction of the piezoelectric element 330 and the dust removing apparatus 310 is driven in the seventh vibration mode. 5 shows a state in which an out-of-plane vibration is generated in the diaphragm 320 by applying an AC voltage having a phase opposite to that of the pair of piezoelectric elements 330 to the left and right. The dust removing apparatus 310 is driven in the sixth vibration mode. The dust removing device 310 of the present invention is a device that can effectively remove the dust attached to the surface of the diaphragm by selectively using at least two vibration modes.

As described above, the piezoelectric element of the present invention is suitably applicable to a liquid discharge head, an ultrasonic motor, and a dust removing apparatus.

Lead-based piezoelectric ceramics containing at least one compound selected from Ba ₄ Ti ₁₂ O ₂₇ and Ba ₆ Ti ₁₇ O ₄₀ of the present invention can be used to achieve a nozzle density equal to or higher than that in the case of using a piezoelectric ceramics containing lead, And a liquid discharge head having a throughput.

Based piezoelectric ceramics containing at least one compound selected from Ba ₄ Ti ₁₂ O ₂₇ and Ba ₆ Ti ₁₇ O ₄₀ of the present invention is used to provide a driving force equal to or higher than that in the case of using a piezoelectric ceramics containing lead, Can be provided.

Based piezoelectric ceramics containing at least one compound selected from Ba ₄ Ti ₁₂ O ₂₇ and Ba ₆ Ti ₁₇ O ₄₀ of the present invention is used to achieve a dust removal efficiency equal to or higher than that in the case of using a piezoelectric ceramics containing lead The branch can provide a dust removal device.

The piezoelectric ceramics of the present invention can be used in devices such as ultrasonic vibrators, piezoelectric actuators, piezoelectric sensors, and ferroelectric memories in addition to liquid discharge heads and motors.

As described above, the piezoelectric element of the present invention is suitably used for a liquid discharge head and an ultrasonic motor. The liquid discharge head includes a non-lead-based piezoelectric element having barium titanate as its main component. Therefore, it is possible to provide a head having a nozzle density equal to or higher than that of the lead-based piezoelectric element and a ground output. Also, the ultrasonic motor may include a non-lead-based piezoelectric element having barium titanate as its main component. Accordingly, it is possible to provide a motor having a driving force and durability equal to or higher than that of the lead-based piezoelectric element.

The piezoelectric ceramics of the present invention can be used in devices such as an ultrasonic vibrator, a piezoelectric actuator, and a piezoelectric sensor in addition to a liquid discharge head and a motor.

(Examples)

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited by the following examples.

Example 1 (Manufacturing Method 1 of Ceramic)

Barium carbonate, titanium oxide, and manganese oxide were used as raw materials and the weight ratio of Ba and Ti was adjusted to 1: 1 so that the addition amount of manganese was 0.12 mass% with respect to the sum of the mass of barium oxide and titanium oxide in terms of metal did. Then, these raw materials were mixed. The resultant mixed powder was calcined at 900 캜 to 1100 캜 for 2 hours to 5 hours.

Subsequently, 3% by mass of PVA was added as a binder to the calcined powder, and the resulting mixture was spray-dried to obtain granulated powder. Then, 0.9 mass% of Ba ₄ Ti ₁₂ O ₂₇ was added to the granulated powder and mixed.

Next, the obtained powder was filled in a mold and then compressed to form a molded article. The resultant shaped body was sintered from 1300 ° C to 1400 ° C for 2 hours to 6 hours to obtain a ceramic. Here, the temperature rise rate was set at 10 占 폚 / min, and the thermocouple of the electric furnace was adjusted so that overshoot of 10 占 폚 or more did not occur from the sintering temperature.

The resultant sintered body was polished so as to have a thickness of 1 mm. Thereafter, the sintered body was heat-treated in the atmosphere from 450 DEG C to 1100 DEG C for 1 hour to 3 hours to remove the organic component from the surface of the sintered body.

Example 2 (Manufacturing Method 2 of Ceramic)

Barium carbonate, titanium oxide, and manganese oxide were used as raw materials and the weight ratio of Ba and Ti was adjusted to 1: 1 so that the addition amount of manganese was 0.12 mass% with respect to the sum of the mass of barium oxide and titanium oxide in terms of metal did. Thereafter, these raw materials were mixed. The resultant mixed powder was calcined at 900 캜 to 1100 캜 for 2 hours to 5 hours.

Subsequently, 3% by mass of PVA was added as a binder to the calcined powder, and the resulting mixture was spray-dried to obtain granulated powder. Thereafter, it was added 0.85% by weight of Ba ₆ Ti ₁₇ 0 ₄₀ minutes for assembly, and mixed.

Next, the obtained powder was filled in a mold and then compressed to form a molded article. The resulting compact was sintered from 1300 ° C to 1400 ° C for 2 hours to 6 hours to obtain a ceramic. Here, the temperature rise rate was set at 10 占 폚 / min, and the thermocouple of the electric furnace was adjusted so that overshoot of 10 占 폚 or more did not occur from the sintering temperature.

The resultant sintered body was polished so as to have a thickness of 1 mm. Thereafter, the sintered body was heat-treated in the atmosphere from 450 DEG C to 1100 DEG C for 1 hour to 3 hours to remove the organic component from the surface of the sintered body.

Example 3 (Manufacturing Method 3 of Ceramic)

Barium carbonate, titanium oxide, and manganese oxide were used as raw materials and the weight ratio of Ba and Ti was adjusted to 1: 1 so that the addition amount of manganese was 0.12 mass% with respect to the sum of the mass of barium oxide and titanium oxide in terms of metal did. Thereafter, these raw materials were mixed. The resultant mixed powder was calcined at 900 캜 to 1100 캜 for 2 hours to 5 hours.

Subsequently, 3% by mass of PVA was added as a binder to the calcined powder, and the resulting mixture was spray-dried to obtain granulated powder. Thereafter, Ba ₄ Ti ₁₂ O ₂₇ and Ba ₆ Ti ₁₇ 0 ₄₀ were added in amounts of 0.45 mass% in the granulated powder and mixed.

Next, the obtained powder was filled in a mold and then compressed to form a molded article. The resulting compact was sintered from 1300 ° C to 1400 ° C for 2 to 6 hours to obtain a ceramic. The temperature rise rate was set at 10 占 폚 / min and the thermocouple of the electric furnace was adjusted so that overshoot of 10 占 폚 or more did not occur from the sintering temperature.

The resultant sintered body was polished so as to have a thickness of 1 mm. The sintered body was heat-treated in the atmosphere from 450 ° C to 1100 ° C for 1 hour to 3 hours to remove organic components from the surface of the sintered body.

Examples 4 to 10 (Manufacturing Method 4 of Ceramic)

Barium carbonate, titanium oxide and manganese oxide were used as raw materials, and the amounts of Ba and Ti were 1: 1, and the amounts of manganese added were as shown in Table 1. Thereafter, these raw materials were mixed. The resultant mixed powder was calcined at 900 캜 to 1100 캜 for 2 hours to 5 hours.

Subsequently, 3% by mass of PVA was added as a binder to the calcined powder, and the resulting mixture was spray-dried to obtain granulated powder. Thereafter, titanium oxide (TiO ₂ ) having an average particle size of 10 nm to 30 nm was mixed with the granulation powder, and the resulting powder was filled in a mold and compressed to form a molded article.

Next, the resulting molded body was sintered from 1300 占 폚 to 1450 占 폚 for 2 hours to 6 hours to obtain a ceramic. The temperature rise rate was set at 10 占 폚 / min and the thermocouple of the electric furnace was adjusted so that overshoot of 10 占 폚 or more did not occur from the sintering temperature.

The resultant sintered body was polished so as to have a thickness of 1 mm. The sintered body was heat-treated in the atmosphere from 450 ° C to 1100 ° C for 1 hour to 3 hours to remove organic components from the surface of the sintered body.

Comparative Example 1 (Production Method 5 of Ceramic)

Barium carbonate, titanium oxide, and manganese oxide were used as raw materials and the weight ratio of Ba and Ti was adjusted to 1: 1 so that the addition amount of manganese was 0.12 mass% with respect to the sum of the mass of barium oxide and titanium oxide in terms of metal did. Thereafter, these raw materials were mixed. The resultant mixed powder was calcined at 900 캜 to 1100 캜 for 2 hours to 5 hours.

Subsequently, 3% by mass of PVA was added as a binder to the calcined powder, and the resulting mixture was spray-dried to obtain granulated powder. The assembly was filled in a mold and then compressed to form a molded article.

The resulting compact was sintered from 1300 ° C to 1400 ° C for 2 hours to 6 hours to obtain a ceramic. The temperature rise rate was set at 10 占 폚 / min and the thermocouple of the electric furnace was adjusted so that overshoot of 10 占 폚 or more did not occur from the sintering temperature.

The resultant sintered body was polished so as to have a thickness of 1 mm. The sintered body was heat-treated in the atmosphere from 450 ° C to 1100 ° C for 1 hour to 3 hours to remove organic components from the surface of the sintered body.

Table 1 shows the production conditions of the piezoelectric ceramics of Examples 1 to 10. In the table, "Mn amount" indicates the amount of manganese weighed.

Table 1: Manufacturing Conditions of Piezoelectric Ceramics

(Structural Evaluation of Piezoelectric Ceramics)

The structure of the crystal grains and grain boundaries of the obtained piezoelectric ceramics was evaluated using a transmission electron microscope (TEM).

First, the crystal structure of crystal grains in each piezoelectric ceramic was evaluated using an electron beam diffraction image. In Examples 1 to 10 and Comparative Example 1, the crystal grains were each formed of BaTiO ₃ having a perovskite structure containing Mn. Mn contained in the crystal grains was measured using an electron beam probe microanalyzer (EPMA). In addition, the crystal grain size was evaluated using a scanning electron microscope.

Furthermore, the composition of the entire piezoelectric ceramics was evaluated by X-ray fluorescence analysis (XRF).

The piezoelectric ceramics were evaluated for grain boundary portions. Specifically, the ratio of the grain boundary portion in the piezoelectric ceramics, the crystal structure contained in the grain boundaries, the presence or absence of Mn in the crystal, and the amount of Mn contained in the grain boundaries were measured.

A procedure for preparing a sample for observing a piezoelectric ceramic using a transmission electron microscope will be described. First, a metal or a carbon film is laminated on the surface of a piezoelectric ceramics whose surface is mirror-polished. This coating was formed to prevent the accumulation of electric charges on the surface of the piezoelectric ceramic during the production process of the thin foil sample for TEM. Next, a thin flake sample having a thickness of 1 m, a width of 10 m and a length of 5 m is cut out from the surface of the piezoelectric ceramics using a concentrated ion beam. The sample was attached to a grid for TEM observation. The sample was irradiated with a focused ion beam parallel to the longitudinal direction of the sample, and the sample was processed to have a thickness of about 100 nm in a region of about 5 mu m in length. The transmission electron microscope observation was carried out by irradiating the electron beam in the thickness direction of the sample (thickness 1 占 퐉 占 10 占 퐉 占 length 5 占 퐉).

The electron diffraction image of the grain boundaries was obtained using the limited field diffraction method. Simultaneously, the barium titanate crystal grain portion (BaTiO ₃ ) was observed under the same conditions to define the camera constant. The lattice spacing was calculated from the resultant diffraction image of the grain boundary portion. The electron diffraction image observation was carried out while arbitrarily changing the inclination angle of the sample to obtain several diffraction images from the same place of the grain boundaries. The lattice plane spacing of each diffraction image was calculated and compared with known document data to specify the grain boundary crystal structure. The grain boundary portion was subjected to composition analysis by the STEM-EDX method to calculate the concentration of Mn contained in the grain boundary portion. "STEM-EDX" is a technique of measuring the intensity of X-ray fluorescence in an arbitrary place on a sample observed by scanning transmission electron microscopy (STEM) with energy dispersive X-ray spectroscopy (EDX).

Table 2 lists the crystal grains of the obtained piezoelectric ceramics and physical properties of grain boundaries.

(Evaluation of the content of the physical properties of the grain boundary)

A: Ba ₄ Ti ₁₂ O ₂₇ only.

B: Ba ₆ Ti ₁₇ 0 ₄₀ alone.

C: Ba ₄ Ti ₁₂ O ₂₇ and Ba ₆ Ti ₁₇ O ₄₀ .

X: No crystal structure of either Ba ₄ Ti ₁₂ O ₂₇ or Ba ₆ Ti ₁₇ O ₄₀ was observed.

(Evaluation of the presence or absence of Mn in the physical properties of the grain boundary)

0: Mn was present in the crystal contained in the grain boundaries.

X: Mn was not present in the crystals contained in the grain boundaries.

In addition, the results of composition analysis by XRF (although not shown in the table) revealed that the molar ratio of Ba to Ti was 1.0: 1.0 in each of Examples 1 to 10 and Comparative Example 1.

Table 2: Properties of crystal grains and grain boundaries

(Grain boundary ratio)

The grain boundary ratio represents the ratio (area%) of at least one compound selected from Ba ₄ Ti ₁₂ O ₂₇ and Ba ₆ Ti ₁₇ O ₄₀ contained in the grain boundary.

As a result of observation of the surface by SEM, it was found that the sub-particles were observed with a contrast different from that of the crystal grains. Based on the results of the above SEM observation, in order to measure the ratio of at least one compound selected from Ba ₄ Ti ₁₂ O ₂₇ and Ba ₆ Ti ₁₇ O ₄₀ contained in the grain boundary to the entire piezoelectric ceramics, Was performed. That is, the surface of the piezoelectric ceramic was observed by SEM, and the crystal grain portion and the subparticle portion were binarized on the basis of the difference of the contrast of the both, and the area of both of them was measured. In order to simplify the measurement, the area of the SEM images taken was calculated for each of 10 sets. The above-described analysis was performed on a region considered to be wide enough for the distribution of the sub-particles in the piezoelectric ceramics. The content (area%) of the sub-particles in the piezoelectric ceramics was calculated by comparing the total of the areas of the sub-particles obtained by the above-described analysis and the areas of the above-mentioned crystal grains.

Fig. 8B is an electron diffraction image obtained by TEM-limited field diffraction of Example 5. Fig. 8A is a [100] incident electron beam diffraction pattern of Ba ₄ Ti ₁₂ O ₂₇ calculated from document data. By comparing the lattice plane spacings of both, it was confirmed that the sub-particles contained Ba ₄ Ti ₁₂ O ₂₇ . Likewise, it was confirmed in each of Examples 1, 3, 4, and 6 to 10 as well.

Table 3 shows the result of comparison between the lattice spacing obtained from the electron diffraction image observed using the above-described limited field diffraction method and the lattice spacing obtained from the known literature data of Ba ₄ Ti ₁₂ O ₂₇ . In the following table, it is known that Ba ₄ Ti ₁₂ O ₂₇ exists in the piezoelectric ceramics of the present invention.

Table 3: Comparison of surface spacing ([100] incident electron diffraction pattern of Ba ₄ Ti ₁₂ 0 ₂₇ )

Fig. 9B is an electron diffraction pattern obtained by TEM-limited field diffraction of grain boundaries in the piezoelectric ceramics of Example 5. Fig. 9A is an [011] incident electron diffraction pattern of Ba ₆ Ti ₁₇ 0 ₄₀ calculated from document data. By comparing the lattice plane spacings of both, it was confirmed that the sub-particles contained Ba ₆ Ti ₁₇ 0 ₄₀ . Likewise, Examples 2 to 4 and 6 to 10 were also confirmed.

Table 4 shows the result of comparison between the lattice spacing obtained from the electron diffraction image observed by the above-mentioned limited field diffraction method and the lattice spacing obtained from the known literature data of Ba ₆ Ti ₁₇ 0 ₄₀ .

Table 4: Comparison of surface spacing ([011] incident electron beam diffraction pattern of Ba ₆ Ti ₁₇ 0 ₄₀ )

In Comparative Example 1, none of the crystal structures of Ba ₄ Ti ₁₂ O ₂₇ and Ba ₆ Ti ₁₇ O ₄₀ was observed in the grain boundary. Therefore, it is known that the amount of Mn contained in the crystal grains is smaller than the amount of Mn that is weighed. On the other hand, in Examples 1 to 10, the amount of Mn weighed and the amount of Mn of the crystal grains were almost the same. It is considered that Mn contained in the crystal grains is efficiently contained because it contains at least one of Ba ₄ Ti ₁₂ O ₂₇ and Ba ₆ Ti ₁₇ O _{40 in} the grain boundary.

Further, the Mn content in the grain boundary portion in each of Examples 1 to 10 was measured. Specifically, the grain boundaries were measured at a plurality of points by combining the crystal structure by the limited field diffraction method and the energy dispersive spectroscopy. As a result, manganese was not included in either of Ba ₄ Ti ₁₂ 0 ₂₇ and Ba ₆ Ti ₁₇ 0 ₄₀ only in Example 4. Further, in Examples 3 and 5 to 10, it was found that manganese was contained in the region of Ba ₄ Ti ₁₂ O ₂₇ by 1 mass% on average in comparison with Ba ₆ Ti ₁₇ O ₄₀ in the crystal structure of Ba ₄ Ti ₁₂ O ₂₇ . Thus, for example, by adding Ba ₄ Ti ₁₂ O ₂₇ particles to the granulated powder, the piezoelectric ceramics in which the grain size is occupied by Ba ₄ Ti ₁₂ O ₂₇ is produced, whereby the precipitation of manganese out of the crystal grains of the piezoelectric ceramics Can be effectively prevented.

(Evaluation of Piezoelectric Properties of Ceramic)

In order to evaluate the piezoelectric characteristics of the piezoelectric ceramics, gold electrodes were formed on both surfaces of the front and back surfaces of the piezoelectric ceramics by the DC sputtering method. Thereafter, the electrode-attached ceramic was cut into a rectangular shape (strip ceramic) having a size of 10 mm x 2.5 mm x 1 mm.

The resultant strip ceramic was polarized. The polarization was carried out at a temperature of 100 占 폚 under the conditions of a polarization voltage of 1 kV DC and a voltage application time of 30 minutes.

Piezoelectric constant was measured using a polarized strip ceramic. Specifically, the impedance dependency of the impedance of the ceramic sample was measured using an impedance analyzer apparatus (trade name: 4294A, manufactured by Ajient). Then, the piezoelectric constant d ₃₁ (pm / V) and the mechanical quality factor Q _m were obtained from the observed resonance frequency and anti-resonance frequency. The piezoelectric constant d ₃₁ has a negative value, and the larger the absolute value, the higher the piezoelectric performance. Further, the mechanical quality factor Q _m means that the loss of the resonance vibration of the resonator is smaller as the absolute value is larger.

Table 5 lists the evaluation results of the piezoelectric characteristics.

Table 5: Piezoelectric properties

As is apparent from Table 5, Ba ₄ Ti ₁₂ O ₂₇ and Ba ₆ Ti ₁₇ O ₄₀ It was found that the piezoelectric constant d ₃₁ and the mechanical quality factor Q _m can be improved together.

(Liquid discharge head according to example 1)

Using the piezoelectric ceramics as in Example 1, the liquid discharge head shown in Figs. 1A and 1B was produced. The discharge of the ink from the liquid discharge head was confirmed in accordance with the inputted electric signal.

(Ultrasonic motor according to example 1)

The ultrasonic motor shown in Figs. 2A and 2B was manufactured by using the piezoelectric ceramics as shown in Example 1. Fig. The rotational action of the motor was confirmed by the application of the AC voltage.

(Dust removal device according to example 1)

Using the same piezoelectric ceramics as in Example 1, the dust removing apparatus shown in Figs. 3A and 3B was produced. When plastic beads were sprayed and an AC voltage was applied, a good dust removal rate was confirmed.

The piezoelectric ceramic of the present invention has good piezoelectric performance and mechanical quality factor. Further, the piezoelectric ceramics of the present invention are environmentally clean. Therefore, the piezoelectric ceramics can be used in a device that uses a piezoelectric ceramics such as a liquid discharge head, an ultrasonic motor, and a piezoelectric device.

While the present invention has been described with reference to exemplary embodiments, it will be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be construed broadly to include structures and functions equivalent to all variations.

This application claims the benefit of Japanese Patent Application No. 2010-285742, filed on December 22, 2010, which is hereby incorporated by reference in its entirety.

101 piezoelectric element
102 Individual Liquid Room
103 Diaphragm
104 Liquid separation wall
105 outlet
106 communication hole
107 common liquid room
108 buffer layer
1011 first electrode
1012 Piezoelectric Ceramic
1013 second electrode
201 oscillator
202 rotor
203 Output shaft
204 oscillator
205 rotor
206 spring
2011 elastic ring
2012 Piezoelectric elements
2013 Organic adhesive
2041 Metal elastomer
2042 Laminated piezoelectric element
310 Dirt remover
330 piezoelectric element
320 diaphragm
331 Piezoelectric ceramics
332 First electrode
333 Second electrode
336 First electrode surface
337 Second electrode face
401 Crystal particles of barium titanate
402 Boundary between crystal grains
403 Triple point
404 Particles present at the boundary between crystal grains
405 Boundaries between crystal grains and minor particles present at triple points
406 Particles present in the triple point
501 Crystal particles of barium titanate
502 particles
503 Crystal particles of barium titanate
504 part particles

Claims (12)

In piezoelectric ceramics,
Crystal grains; And
And the crystal grains contain 0.04 mass% or more and 0.20 mass% or less of manganese in terms of metal with respect to barium titanate of the perovskite type structure and barium titanate, respectively,
Wherein the grain boundary contains at least one compound selected from the group consisting of Ba ₄ Ti ₁₂ O ₂₇ and Ba ₆ Ti ₁₇ O ₄₀ ,
Manganese is included in the crystals contained in the grain boundaries,
Wherein the ratio of at least one compound selected from the group consisting of Ba ₄ Ti ₁₂ O ₂₇ and Ba ₆ Ti ₁₇ 0 ₄₀ contained in the grain boundary when observed on the surface or cross section of the piezoelectric ceramic is a surface or cross section of the piezoelectric ceramics Is not less than 0.05% by area and not more than 2% by area based on the total area of the piezoelectric ceramic.
delete The method according to claim 1,
Wherein the grain boundary contains Ba ₄ Ti ₁₂ O ₂₇ or Ba ₆ Ti ₁₇ O ₄₀ ,
Wherein all of the Ba ₄ Ti ₁₂ O ₂₇ and Ba ₆ Ti ₁₇ O ₄₀ contain manganese.
The method according to claim 1,
Wherein the grain boundary contains Ba ₄ Ti ₁₂ O ₂₇ and Ba ₆ Ti ₁₇ O ₄₀ ,
Wherein each of Ba ₄ Ti ₁₂ O ₂₇ and Ba ₆ Ti ₁₇ O ₄₀ contains manganese.
5. The method of claim 4,
Wherein the content of manganese contained in the Ba ₄ Ti ₁₂ O ₂₇ is larger than the content of manganese contained in Ba ₆ Ti ₁₇ O ₄₀ .
The method according to claim 1,
When the content of manganese to be contained in at least one compound selected from the group consisting of Ba ₄ Ti ₁₂ 0 ₂₇ and Ba ₆ Ti ₁₇ 0 ₄₀ to be contained in the grain boundary phase, consisting of Ba ₄ Ti ₁₂ 0 ₂₇ and Ba ₆ Ti ₁₇ 0 ₄₀ And not less than 0.6 mass% and not more than 2.8 mass% in terms of the metal, based on the at least one compound selected from the group consisting of the metals.
A step of adding a binder to barium titanate particles containing manganese in an amount of 0.04 mass% or more and 0.20 mass% or less in terms of metal; And
And sintering a mixture prepared by adding at least one compound selected from the group consisting of Ba ₄ Ti ₁₂ O ₂₇ particles and Ba ₆ Ti ₁₇ O ₄₀ particles to the granulated powder.
A step of adding a binder to barium titanate particles containing manganese in an amount of 0.04 mass% or more and 0.20 mass% or less in terms of metal; And
And a step of sintering the mixture prepared by adding titanium oxide particles having an average particle size of 100 nm or less to the granulated powder.
A first electrode;
Piezoelectric ceramics; And
As a piezoelectric element having a second electrode,
Wherein the piezoelectric ceramics is the piezoelectric ceramic according to claim 1.
A liquid discharge head using the piezoelectric element according to claim 9.
An ultrasonic motor using the piezoelectric element according to claim 9.
A dust removing apparatus using the piezoelectric element according to claim 9.

Images